WO2015072001A1

WO2015072001A1 - Superconducting magnet

Info

Publication number: WO2015072001A1
Application number: PCT/JP2013/080847
Authority: WO
Inventors: 照久宮副; 武中山; 竜弥安藤; 学青木
Original assignee: 株式会社日立製作所
Priority date: 2013-11-15
Filing date: 2013-11-15
Publication date: 2015-05-21
Also published as: US9852831B2; US20160268028A1; JPWO2015072001A1; JP6215345B2

Abstract

The purpose of the present invention is to provide a method for detecting an increase of a temperature due to normal conduction transition of a superconducting coil, said method making it possible to suppress deterioration of superconducting characteristics, to reduce an electrical connection area, and to select a region to be detected. This superconducting magnet includes: a superconducting coil that is formed by winding a first superconducting wire rod; a second superconducting wire rod, which is disposed by being thermally in contact with and electrically insulated from the superconducting coil, and which has a superconducting transition temperature that is lower than that of the first superconducting wire rod; voltage terminals that are disposed at a plurality of areas of the second superconducting wire rod; a voltmeter connected to the voltage terminals; and a switch circuit connected to the voltmeter. The switch circuit interrupts a current when receiving an output from the voltmeter, said current being to be supplied to the superconducting coil.

Description

Superconducting magnet

The present invention relates to a superconducting magnet.

As a background art in this technical field, there is JP 2012-238628 A (Patent Document 1). In this publication, “Providing a high-temperature superconducting magnet capable of detecting the occurrence of quench, which is a normal transition phenomenon of a superconducting coil, with high accuracy, and quickly detecting the occurrence of quench and performing a protective operation. For this purpose, a superconducting magnet is wound with a parallel conductor in which two or more conductors constituting the parallel conductor are electrically connected to each other, and a voltage terminal is connected to each superconducting wire in the electrically connected section of the parallel conductor. "The occurrence of quenching is detected by installing and observing the potential difference."
Further, there is JP-A-8-304271 (Patent Document 2). In this publication, “at the initial stage of quench generation, it is possible to sense the minute change and to provide a quench generation detection apparatus and detection method capable of observing the change of the entire system. In the device for detecting the quench of the superconducting wire, the quench is detected from the superconducting wire, the optical fiber wound around the superconducting wire, the light source for making the deflected light incident on the optical fiber, and the device for detecting the polarized light from the optical fiber. Are listed.

JP 2012-238628 A JP-A-8-304271

However, the configuration of the superconducting coil becomes complicated if it is attempted to install voltage terminals for each section, for example, by soldering. In addition, when performing quench detection with a deflected light beam, a plurality of polarizing plates and mirrors are required to produce the deflected light beam, which complicates the measurement system.

Therefore, an object of the present invention is to provide a superconducting magnet that can detect a temperature rise accompanying the normal conduction transition of a superconducting coil with a simple structure.

In order to solve the above problems, for example, the configuration described in the claims is adopted.
The present application includes a plurality of means for solving the above-mentioned problems. For example, "a superconducting coil formed by winding a first superconducting wire, and being in thermal contact with the superconducting coil; and A second superconducting wire that is electrically insulated and has a lower superconducting transition temperature than the first superconducting wire, a voltage terminal installed at a plurality of locations of the second superconducting wire, and the voltage A voltmeter connected to a terminal, and a switch circuit connected to the voltmeter, the switch circuit receiving an output of the voltmeter and cutting off a current supplied to the superconducting coil. Features.

The present invention can provide a superconducting magnet having a simple structure and capable of detecting a temperature rise accompanying the normal conduction transition of the superconducting coil.

It is a block diagram of the superconducting coil which detects the temperature rise regarding Example 1 of this invention. It is an example of the circuit diagram of the superconducting magnet which detects the temperature rise regarding Example 1 of this invention. It is an example of the block diagram of the superconducting coil which detects the temperature rise which does not require a voltage terminal inside the coil | winding regarding Example 2 of this invention. It is an example of the circuit diagram of the superconducting magnet which detects the temperature rise which does not require a voltage terminal inside the coil | winding of the superconducting coil regarding Example 2 of this invention. It is an example of the block diagram of the superconducting coil which detects the temperature rise of the selected area | region regarding Example 3 of this invention. It is a basic lineblock diagram of a superconducting magnet.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

The superconducting magnet 1 of the present embodiment will be described with reference to FIGS.

FIG. 6 shows the basic configuration of the superconducting magnet 1. As shown in FIG. 6, the basic configuration of the superconducting magnet is a superconducting coil 2 and a cryostat 36.

The superconducting coil 2 is formed by winding the superconducting wire 16 around a winding frame 26. The end portion of the superconducting wire 16 is connected to the external power source 56 by an external power source 56 and current leads 46 and 47, and the superconducting coil 2 can receive a current from the external power source 56 and generate a magnetic field. .

Further, the superconducting magnet 1 needs to cool the superconducting coil 2 below a certain temperature in order to maintain the superconducting state. In this embodiment, the superconducting coil 2 is invaded by the refrigerant in the cryostat 36, for example, liquid helium. It is kept under low temperature by soaking.

The cooling method may be a method of immersing in a liquid refrigerant or a conductive cooling method using a metal having high thermal conductivity such as pure copper. A refrigerator (not shown) is used for cooling the refrigerant and conducting cooling, and a shielding shield (not shown) is provided so as to cover the superconducting coil 2 in order to block heat intrusion from the outside. Also good.
The superconducting coil 2 is connected to the external power source 56 through the

current leads

46a and 46b as described above. When the superconducting magnet 1 is operated, current is supplied from the external power source 56 to the superconducting coil 2. At this time, if there is any abnormality in the circuit including the superconducting coil 2 and the superconducting coil 2, the current is cut off. There is a need.

In particular, a temperature rise occurs in a part of the superconducting coil 2 for some reason, and this part undergoes a normal conduction transition and electrical resistance is generated, resulting in a phenomenon in which the whole superconducting coil 2 undergoes a normal conduction transition (quenching phenomenon). ) Occurs, it is desirable to quickly stop energization of the superconducting coil 2 and consume the accumulated magnetic energy so that the superconducting coil 2 is not damaged. There are various factors of unexpected normal conduction transition of the superconducting coil 2, such as deterioration of the superconducting coil 2, manufacturing errors, abnormality of the refrigerator, breakage of the shielding shield, and the like.

The following methods can be considered for stopping the energization of the superconducting coil 2 when the abnormality of the superconducting magnet 1 occurs and consuming the accumulated magnetic energy.

For example, the electrical resistance generated by the normal conduction transition of a part of the superconducting coil 2 is detected by measuring the voltage related to the resistance at the

voltage terminals

66a and 66b. As shown in FIG. 6, this voltage measurement can be performed by providing

voltage terminals

66 a and 66 b at the unwinding portion of the superconducting wire 16 that forms the superconducting coil 2.

Then, the voltage measurement result is transmitted to the switch drive circuit 76, and the switch drive circuit 76 that receives the voltage opens the switch 86, whereby the connection between the superconducting coil 2 and the external power source 56 is cut off, and the superconducting coil 2 is connected. Is turned off. Further, when the switch 86 is opened, a closed circuit is formed by the superconducting coil 2 and the protection circuit 96. In this closed circuit, the energy accumulated in the superconducting coil 2 is consumed in the form of heat generation of the protective resistance of the protection circuit 96, and the release of energy due to heat generation of the superconducting coil 2 itself can be suppressed.
FIG. 1 shows a detailed configuration of the superconducting coil 2 in the present embodiment.

In this embodiment, as shown in FIG. 1, the superconducting wire 16 includes a wire 11a as a first superconducting wire and a wire 11b as a second superconducting wire, and the

wires

11a and 11b have different superconducting transition temperatures. Consists of. In the present embodiment, the wire 11a has a superconducting transition temperature higher than the superconducting transition temperature of the wire 11b.

These

wires

11a and 11b are coated with an electrically insulating material 31 such as resin and are electrically insulated from each other, but are in thermal contact with each other. The superconducting coil 2 is formed by winding a conductor 41 made of the wire 11a, the wire 11b, and the electrical insulating material 31.

In the superconducting coil 2 of this embodiment, the coil made of the wire 11a having a high superconducting transition temperature among the two types of

wires

11a and 11b functions as a main superconducting coil whose main purpose is to generate a magnetic field. The coil made of the wire 11b having a low superconducting transition temperature functions as a sub superconducting coil whose main purpose is to detect a temperature rise. The external power source 56 may be connected to the main superconducting coil, and a separate current source may be prepared for the sub superconducting coil and connected thereto.

Voltage terminals

21a and 21b are attached to both ends of the wire 11b, and one voltage terminal 21c is attached to the inside of the winding, that is, in the middle of the wire. Therefore, in the wire 11b, when a normal conduction transition occurs between the voltage terminal 21a and the voltage terminal 21c, a voltage is measured between the terminals, and the normal conduction transition is performed between the voltage terminal 21b and the voltage terminal 21c. When this occurs, the voltage is measured between these terminals.

Hereinafter, the function of detecting the temperature rise of the main superconducting coil by the sub superconducting coil made of the wire 11b will be described.

FIG. 2 is an example of a circuit diagram for detecting the temperature rise of the superconducting magnet.

While the superconducting magnet 1 is operated, the superconducting coil 2 is energized from the external power source 56. Here, when the transition from the superconducting state to the normal conducting state occurs in the wire 11a constituting the main superconducting coil for some reason, the resistance value of the main superconducting coil changes from R ₁ > = 0 to R ₁ > 0.

If the energization current to I _1, in normal conducting transition portion of the primary superconducting coil, heat generation of the R ₁ I ₁ ² is produced. Since the generated heat is transmitted to the part other than the part where the normal conduction transition is first performed, the region where the temperature exceeds the superconducting transition temperature in the wire 11a, that is, the normal conduction transition region expands. As a result, R _{1 of the} main superconducting coil becomes It increases according to the elapsed time.

On the other hand, the heat generated by the wire 11a also propagates to the wire 11b that is in thermal contact with the wire 11a. As a result, a normal conduction transition also occurs in the wire 11b, and the resistance R _2a or R _2b is also generated in the sub superconducting coil made of the wire 11b. If the current flowing through the sub superconducting coil is I ₂ , the amount of heat generated in the wire 11b is R _2a I ₂ ² or R _2b I ₂ ² , and this heat generation expands the normal conduction transition region in the sub superconducting coil. As a result, the resistance values (R _2a , R _2b ) of the sub superconducting coil made of the wire 11b also increase according to the elapsed time.

Thus, when the normal conduction transition occurs in the superconducting coil 2, the normal conduction transition region expands in both the main superconducting coil and the sub superconducting coil. However, since the wire 11b has a lower superconducting transition temperature than the wire 11a, the heat capacity until the normal conduction transition is small. Therefore, the propagation speed of the normal conduction transition region of the wire 11b is higher than that of the wire 11a.

For example, when the wire 11b is a niobium titanium wire and the wire 11a is a bismuth-based copper oxide superconducting wire, the propagation speed of the normal transition region of the wire 11b can be 1000 times or more the several mm / s that is the propagation speed of the wire 11a.

Since the magnitude of the generated voltage in the superconducting coil depends on the width of the normal transition region, it increases with the propagation of the normal transition region. For this reason, the generated voltage in the sub-superconducting coil made of the wire 11b is increased at a higher rate than the generated voltage in the main superconducting coil made of the wire 11a whose heat capacity until the normal conduction transition is larger than that of the wire 11b.

Therefore, in the superconducting magnet 1 of the present embodiment, the generated voltage in the sub superconducting coil made of the wire 11b is measured, and the switch 86 is opened through the switch driving circuit 76 according to the voltage value, and the external power source 56, the superconducting coil 2, and the like. Disconnect the connection. As a mechanism for interrupting the connection between the external power source 56 and the superconducting coil 2 and interrupting the supply of current to the superconducting coil 2 or the main superconducting coil, a circuit breaker may be used instead of the switch 86. For the above reasons, the superconducting magnet 1 of the first embodiment does not necessarily require an electrical connection for detecting the voltage of the main superconducting coil.

After shutting off the external power supply 56, the magnetic energy 0.5 L ₁ I ₁ ² accumulated in the main superconducting coils made of wire 11a is released by the relaxation time of L ₁ / R _s by the protective resistor R _s.

Further, when there is a certain difference in the superconducting transition temperature between the wire 11a and the wire 11b, the main superconducting power is detected even if the temperature rise is confirmed in the main superconducting coil but the normal conducting transition has not yet occurred. Since the normal conduction transition of the sub superconducting coil derived from the heat propagated from the coil can be detected, the superconducting magnet 1 can be stopped at a stage where the load applied to the main superconducting coil is small.

Further, the mounting position of the voltage terminal 21c may be a position where L _2a = L _{2b as} shown in FIG. 2 in order to cancel the inductance L ₂ (= L _2a + L _2b ) due to winding. Specifically, since the

voltage terminals

21a and 21b are installed at both ends of the wire 11b, for example, in the vicinity of the unwinding port, the voltage terminal 21c is installed at a position corresponding to the midpoint between the

voltage terminals

21a and 21b. It will be good.

By arranging the

voltage terminals

21a, 21b, and 21c in this way, the difference between the voltages generated at L _2a and L _2b can be measured. If the difference is 0, no resistance is generated due to temperature rise, Further, when the difference is detected, it is possible to detect the abnormality of the wire 11a with high accuracy on the assumption that resistance due to a temperature rise has occurred.

Further, when the superconducting magnet 1 is operating normally, the voltage measured between the voltage terminal 21a and the voltage terminal 21b is measured, and the difference between the reference voltage and the voltage measured in real time is obtained. The temperature rise of the wire rod 11a may be detected. In this case, since it is not necessary to install the voltage terminal 21c, the mechanism for detecting the temperature rise of the main superconducting coil can be simplified.

As described above, the superconducting magnet 1 of this embodiment is configured to connect the wound superconducting wires in parallel to each other in order to detect the generated voltage of the main superconducting coil, or to divide the superconducting wires into fine voltage terminal pairs. There is no need to provide it, and the generated voltage can be detected with a simple structure.

If the wire 11a and the wire 11b are in thermal contact, the voltage terminal pair does not have to be attached to the main superconducting coil made of the wire 11a. That is, since heat due to soldering is not applied to the wire 11a, it is possible to prevent deterioration of the superconducting characteristics of the wire 11a.

For example, when the wire 11a is a so-called high-temperature superconducting wire such as a bismuth-based copper oxide wire or an yttrium-based copper oxide wire, if the heat is applied by a soldering iron of 200 ° C. or higher, the superconducting characteristics are deteriorated. May occur. However, since this embodiment can reduce the number of soldered connections, it is particularly effective in reducing the deterioration factor of the superconducting characteristics when manufacturing a superconducting coil that uses a high-temperature superconducting wire as the main wire.

In this embodiment, an example of a superconducting coil capable of detecting a temperature rise not only by a superconducting coil having a voltage terminal disposed inside the winding but also by only a pair of voltage terminals at both ends will be described.
FIG. 3 is an example of a configuration diagram illustrating the superconducting coil in the second embodiment.

In the superconducting coil 2 in FIG. 1, the description of the components having the same functions as those in FIG.

In Example 2, two second

superconducting wires

13b and 13c that are in thermal contact with each other are wound around the wire 11a. The

wires

13b and 13c form two sub superconducting coils having the same inductance L ₂ ′.

Voltage terminals

23a, 23b, 23c, and 23d are provided at both ends of each sub superconducting coil, and the voltages are measured.

FIG. 4 shows an example of a circuit diagram in the second embodiment.

As shown in FIG. 4, reverse currents are passed through the sub-superconducting coils made of the

wires

13b and 13c. In this way, the inductance L ₂ ′ can be canceled by passing the current, and the voltage terminal inside the winding becomes unnecessary. Similarly to the first embodiment, the current of the main superconducting coil made of the wire 11a can be cut off through the switch drive circuit 76 in accordance with the voltage values measured by the

voltage terminal pair

23a, 23b and the

voltage terminal pair

23c, 23d. it can.

In the first embodiment, when the voltage terminal is arranged inside the winding, it is necessary to identify the position where the inductance L _2a = L _2b , but in the second embodiment, the identification work can be omitted and the superconducting coil 2 can be omitted. It is possible to reduce the load required for the production.

A plurality of wires 13b and wires 13c may be prepared and wound around the same number of main superconducting coils. At this time, the number of wires that allow current to flow in one direction and the number of wires that allow current to flow in the opposite direction to the one direction may be the same.

In this embodiment, an example of a superconducting magnet capable of detecting a temperature rise by not only a superconducting magnet in which a second superconducting wire is wound around a first superconducting wire but also a part of the second superconducting wire is in thermal contact with each other. Will be explained.
FIG. 5 is an example of a configuration diagram illustrating the superconducting coil in the third embodiment.

In the superconducting coil of FIG. 1, the description of the components having the same functions as those already described with reference to FIG. 1 is omitted.

In Example 3, the second superconducting wire 35 is contacted from the superconducting coil surface to the outer peripheral surface of the superconducting coil formed of the wound first superconducting wire 11a, that is, the outer peripheral surface of the superconducting coil formed in a cylindrical shape.

Let Voltage terminals

25a and 25b are provided at both ends of the wire 35, the voltage is measured, and the current of the superconducting coil made of the first wire 11a is cut off according to the measured voltage, as in the first or second embodiment. Since the wire 35 is made short, unlike the first or second embodiment, the inductance of the second wire is small, and there is no need to form a circuit for canceling the inductance.

Further, the wire 35 may be installed as follows with respect to the coil made of the wire 11a. First, the wire 35 is arranged so as to be as parallel as possible to the wire 11a. The direction 65 of the current flowing through the wire 35a is the same as the direction of the current flowing through the wire 11a. When the wire 35 is thus arranged and the direction of the current is controlled, the direction 35 of the electromagnetic force acts on the wire 35 due to the direction 55 of the magnetic field generated from the superconducting coil made of the wire 11a. As a result, the wire 35 is subjected to a force pressed against the wire 11a, can reduce the contact thermal resistance between the first and second

superconducting wires

11a, 35, and can increase the detection accuracy of the temperature rise.

In addition, you may provide the detection structure of the generated voltage containing the wire 35 and the

voltage terminals

25a and 25b connected to the both ends in the several location of the superconducting coil which consists of the wire 11a. By providing at a plurality of locations, the temperature rise of the superconducting coil made of the wire 11a can be detected with higher accuracy.

DESCRIPTION OF SYMBOLS 1 Superconducting magnet 2

Superconducting coil

11a, 16

1st superconducting wire

11b, 13b, 13c, 35

2nd superconducting wire

21a, 21b, 21c, 23a, 23b, 23c, 23d, 25a, 25b, 66a, 66b Voltage terminal 31 Electrical insulation material 41 Parallel conductor 45 Direction of electromagnetic force 55 Direction of magnetic field generated by main superconducting coil made of first superconducting wire 65 Direction of current of second superconducting wire 26 Reel 36

Cryostat

46a, 46b Current lead 56 External Power supply 76 Switch drive circuit 86 Switch 96 Protection circuit

Claims

A superconducting coil formed by winding the first superconducting wire,
A second superconducting wire that is in thermal contact with the superconducting coil and is electrically insulated and has a lower superconducting transition temperature than the first superconducting wire;
Voltage terminals installed at a plurality of locations of the second superconducting wire;
A voltmeter connected to the voltage terminal;
A switch circuit connected to the voltmeter,
The switch circuit receives an output from the voltmeter and cuts off a current supplied to the superconducting coil.
The superconducting magnet according to claim 1,
The second superconducting wire is wound together with the first superconducting wire,
The voltage terminal is provided at both ends of the second superconducting wire.
The superconducting magnet according to claim 1,
An even number of second superconducting wires are wound together with the first superconducting wire,
A superconducting magnet, wherein the number of the second superconducting wires in which current flows in one direction and the number of the second superconducting wires in which current flows in a direction different from the one direction are the same.
The superconducting magnet according to claim 1,
The second superconducting wire is a member shorter than the circumference of the outer circumferential surface of the superconducting coil, and is disposed on the outer circumferential surface of the superconducting coil.
The superconducting magnet, wherein the voltage terminal is connected to both ends of the second superconducting wire.
The superconducting magnet according to claim 2,
A voltage terminal is further installed at a midpoint with respect to both ends of the second superconducting wire,
The voltmeter is provided at a first voltmeter connected to a voltage terminal provided at one end and a midpoint of the second superconducting wire, and at the other end and a midpoint of the second superconducting wire. And a second voltmeter connected to the voltage terminal.
The superconducting magnet according to claim 4,
The second superconducting wire is a superconducting magnet in which a current flows in a direction in which a force attracted toward the superconducting coil is applied by an electromagnetic force generated from the superconducting coil.
The superconducting magnet according to any one of claims 1 to 6, wherein
The first superconducting wire and the second superconducting wire are connected to independent current sources, respectively.
The superconducting magnet according to any one of claims 1 to 7,
The superconducting magnet according to claim 1, wherein the switch circuit includes a circuit breaker that interrupts a current supplied to the first superconducting wire.
A superconducting magnet according to any one of claims 1 to 8,
A superconducting magnet characterized by energizing the second wire and detecting heat generation of the superconducting magnet by normal conduction transition of the second wire.